[Elecraft] K2 ATU Question

[Tom Hammond NØSS]

Hi Jeff:

>K2 without ATU puts out, for example, 5 watts on 40 meters into dummy load.
>Installed and aligned ATU. With 5 watts requested, I get about 3 watts out
>into same dummy load and SWR shows close to  1:1. What am I missing?

What are you using to measure the power out? K2's display or an external 
wattmeter of known accuracy?

The 'stock' K2 does not include a true 'wattmeter', only an RF voltmeter 
which may or not indicate accurately, depending upon the actual load being 
presented by the antenna... load impedance higher than 50 Ohms, displayed 
power is generally higher, load impednace lower than 50 Ohms, the displayed 
power is genrally lower.

The KAT2 contains a directional wattmeter circuit which can be calibrated 
acceptably well to much more accurately indicate actual power output. BUT 
you do have to do a creditable job of calibration and you have to decent 
instruments (dummyload and accurate external wattmeter) against which to 
calibrate the wattmeter. Thre are othr ways to calibrate WITHOUT an 
external wattmeter, but you then will have to build an RF probe to use with 
your DMM or DVM.

73,

Tom Hammond   N0SS